I have an older Stihl chainsaw that I believe is a 028 Pro. It looks similar to the MS 280 C. It is about 14 years old and for the last 4 years or so, when cutting into wood, it just seems to lose power. I have rebuilt the carb countless times and have adjusted the idle screws as much as I know to do. I have also been told that it passes the redneck compression test (pick the saw up by the sarter cord, if it does not pull out, good compression). Any other ideas of what I could try? It is my backup saw, but I really like to use it because it is lighter that the Husky's.

If you are satisfied that the carb is clean try readjusting the mixture. Start with both idle and high speed mixture screws one turn out from lightly seated. Start the saw and adjust the idle mixture to achieve the highest idle just below clutch engagement. Allow the saw to warm up and the ajust the idle so that there is smooth acceleration to full throttle. Do not lean out the mixture too far. Adjust the high speed mixture slowly to achieve the optimum performance under load. Make sure that the muffler and exhaust port is unrestricted. Remove and clean if necessary. If the problem continues it would indicate that the rings are not sealing properly or that the crankcase is not properly sealed. A simple compression check with a guage will tell you the condition of the cylinder and rings. If the engine has good compression the next step would be to pressure test the crankcase. This is not a hard thing to do but you will need a guauge and pump to pressurize it and you will need to seal the exhaust port. You will also have to find a way to seal the intake and attach the guage and pump there. Once pressurized you can check seals, gaskets and the crankcase itself with soap and water. Just like trying to find a hole in a tire. If there are leaks, air is getting pulled into the crankcase and making the fuel mixture leaner. If you don't have access to the tools necessary you might be better off taking the saw in to a local repair shop for testing.